module Roda::RodaPlugins::ErrorHandler

def self.configure(app, opts={}, &block)

the Roda class with it.
If a block is given, automatically call the +error+ method on 
def self.configure(app, opts={}, &block)
  app.opts[:error_handler_classes] = (opts[:classes] || app.opts[:error_handler_classes] || DEFAULT_ERROR_HANDLER_CLASSES).dup.freeze
  if block
    app.error(&block)
  end
end